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1 Ciência Téc. Vitiv. 27 (2) VINEYARD WEED COMMUNITY DYNAMICS IN THE DÃO WINEGROWING REGION DINÂMICA DA VEGETAÇÃO INFESTANTE DAS VINHAS DA REGIÃO VITIVINÍCOLA DO DÃO Ana Monteiro*, Fátima Caetano, Teresa Vasconcelos, Carlos M. Lopes Instituto Superior de Agronomia, Universidade Técnica de Lisboa, Centro de Botânica Aplicada à Agricultura, Tapada da Ajuda, Lisbon, Portugal, Correspnding author: Tel.: ; Fax: , (Manuscrito recebido em Aceite para publicação em ) SUMMARY With the aim of analysing the influence of both the sub-region and weed-control practices on vegetation composition and dynamics in the Portuguese Dão Winegrowing Region, 120 vineyards were surveyed for weeds and winegrowers were asked to respond to a questionnaire in taxa distributed across 31 families were recorded, with a predominance of Fabaceae, Asteraceae and Poaceae. The predominant vineyard inter-row soil management techniques were cover cropping (53%), with some cover sown but mostly relying on resident vegetation, and soil tillage (31%). Herbicides were applied in the row in 46%, and in the overall area in 4%, of the vineyards. Canonical correspondence analysis revealed significant effects of the sub-region and the different soil management strategies on vineyard community structure. Compared with the last (and only) study, which took place in 1950, weed composition was different and species diversity increased. The present study showed that resident vegetation also increased plant diversity. The dynamics of the perennial weed species Cynodon dactylon and Convolvulus arvensis must be carefully evaluated in order to avoid severe competition with the vine. RESUMO Com o objetivo de avaliar a influência da sub-região e dos métodos de gestão do solo da vinha na composição e dinâmica da vegetação infestante, no final do Inverno de 2008, foram efetuados 120 levantamentos florísticos e inquéritos aos viticultores nas sete sub-regiões da região vitivinícola do Dão. Registaram-se 206 táxones, distribuídos por 31 famílias, com predominância das Fabaceae, Asteraceae e Poaceae. Em mais de metade das vinhas (53%) procedia-se ao enrelvamento na entrelinha, semeado ou, predominantemente, natural, e num terço (31%) à mobilização total. Relativamente à aplicação de herbicidas, em 4% das vinhas fazia-se monda química em toda a área e em 46% aplicavam-se herbicidas na linha. A aplicação da análise canónica de correspondências mostrou que a composição da vegetação infestante presente nas vinhas era influenciada quer pela sub-região quer pela técnica de gestão do solo. Verificou-se um aumento na diversidade florística em relação ao último e único estudo efetuado em O nosso estudo mostrou ainda que o enrelvamento natural também aumentou a diversidade florística. A dinâmica das infestantes perenes como Cynodon dactylon e Convolvulus arvensis, presentes em todos os sistemas de de gestão do solo inventariados, exige um adequado programa de controlo de forma a evitar situações de elevada competição com a videira. Key words: weeds, soil management, biodiversity, Vitis vinifera. Palavras-chave: infestantes, gestão do solo, biodiversidade, Vitis vinifera. INTRODUCTION After the advent of herbicides and until recently, Portuguese vineyard soil management practices typically involved integrating soil tillage in the inter row with post- and pre-emergence herbicides in the row, with less emphasis on the incorporation of other control methods (Monteiro and Moreira, 2004). In the last two decades, vineyard soil management systems have been changing in Portugal; however, information about the importance of the methods applied and their implications for weed community dynamics is scarce. The need to reduce costs and make grape production more sustainable has prompted the use of alternative weed control practices that optimize production while maintaining profits. Cover cropping is consequently gaining popularity among Portuguese winegrowers. Vineyard natural cover cropping can cause significant reductions in vine vegetative growth and yield, because the swards compete with vines for water and nutrients (Afonso et al., 2003; Celette et al., 2008; Lopes et al., 2011; Monteiro et al., 2012). Other studies in Portugal have shown that in some viticultural regions, resident vegetation can also be an important ecological vineyard management tool for controlling vigour and enhancing wine quality (Monteiro and Lopes, 2007; Lopes et al., 2008) and reducing pest densities (Campos et al., 2006). The opinion that plant identification, plant richness (number of species) and diversity (relative abundance of species) play a major role in contributing to human welfare is emerging in land and crop management. Indeed, knowledge of the distribution and infestation of plant communities and the ecological factors involved in their diversity and variability is a determinant factor in rational weed control (Michez and Guillerm, 1984). Species compositional changes have been observed for different weed management systems (Wrucke and Arnold, 1985; Teasdale et al., 1991; Monteiro et al., 2008). Some weed species do not display a unique association with management practices, growing equally well in all systems. Zaragoza et al. (1989) reported that species number can be significantly reduced in no-till herbicide systems, 73

2 but that annual grasses and perennial weed species predominate. The identification of vineyard weeds and their relationship with ecological factors are well documented for most Portuguese winegrowing regions (Cerejeira, 1985; Barata, 1987; Espírito Santo, 1987; Ribeiro, 1988; Lopes, 1989; Moreira, 1990; Aguiar, 1992; Mira et al., 1999; Espírito Santo et al., 2000), but there is a paucity of published research on vineyard weed communities in the Dão winegrowing region. A single study on 26 mostly manually cultivated vineyards was carried out in 1950 (Pinto da Silva, 1971). However, the viticulture of the Dão is of great economic, importance because it covers about ha, or 16% of the region s total agricultural area (Afonso, 2003). There is therefore a need for further studies on weed management strategies across the entire region and the response to them in terms of weed community dynamics. At the same time, sustainable viticulture needs a multistrategy approach where weeds are responsive not only to weed control, but also to numerous other facets of viticulture. When the winegrower chooses a natural (resident vegetation) or sown cover crop, information about plant species that adapt well to the relevant ecological and agronomical factors is fundamental in order to avoid negative impacts on wine grape production. Annual plant species with a short life cycle and auto-sown or perennials that regenerate soon after the first autumn rains, preferably with low water consumption (Lopes et al., 2004), are recommended. There is also a need for research on cover cropping plant species (which are frequently considered to be weeds), as they might enhance biodiversity, wine quality and vineyard aesthetics, all of which are very important to the recent increase in the agro-tourism business. The present project s objectives were thus to use the weed-vineyard and winegrower surveys to: (1) characterize weed composition and density; (2) evaluate the ecological influence (sub-region) on plant-species composition and diversity in order to identify appropriate plant species for cover cropping; and (3) determine which soil management practices are used and their effects on weed community composition. species per survey were then calculated according to Barralis (1976): D = (0.5n1+1.5n2+11.5n3+35.5n4+75.5n5)/ /(n1+n2+n3+n4+n5) (eq. 1) n1, n2, n3, n4, n5 number of surveys where the species presented a density of 1, 2, 3, 4 and 5, respectively; FA = n a (eq. 2) n total number of surveys; a number of surveys where the species was absent; FR = 100*(n a) / n (eq. 3) The weed infestation degree was evaluated according to Michez and Guillerm (1984) in a plot created by the relationship between FR (abscissa) and D (ordinate). Plant species were also grouped according to annual broad-leaved species, annual grass species, perennial broad-leaved species, perennial grass species and other monocotyledons. Canonical correspondence analysis (CCA) was used to elucidate weed community structure and associations, as they might be affected by geographical location (sub-region) and by soil management practices in the inter-row (treatments) (ter Braak and Smilauer, 1998). Analysis was based on weed species density per survey. Treatments were treated as independent variables and species density as dependent variables. The geographic variables were the seven sub-regions: Alva, Besteiros, Castendo, Serra da Estrela, Silgueiros, Terras de Azurara, and Terras de Senhorim. The soil management practice variables were: soil tillage (MOB), chemical control (HERB), resident vegetation (RNA), and sown cover crop (RSE). CCA was performed in CANOCO (Canoco for Windows version 4.5), with axis scores centred to interspecies distances and biplot scaling. Automatic forward selection with Monte Carlo permutation test was used to determine the significance of the treatments. Treatment centroids and canonical coefficients for the species are presented in biplots. Proximity of species score to a treatment centroid signifies that the species had the highest density in that treatment. MATERIAL AND METHODS The study was conducted in commercial vineyards throughout the Dão winegrowing region, Central Portugal, from March until May Vineyardvegetation and winegrower surveys (120) were carried out in the seven Dão sub-regions. The site location of each survey is described by Caetano (2009). Individual plant species density was estimated using the scale proposed by Barralis (1975), where 1 = < 1; 2 = 1 to 2; 3 = 3 to 20; 4 = 21 to 50; and 5 > 51 plants/m -2. The average density (D), absolute frequency (FA) and relative frequency (FR) for each RESULTS AND DISCUSSION Weed vegetation composition and diversity A total of 206 taxa were surveyed in inter-row for the region as a whole (Table I). In 1950, Pinto da Silva (1971) identified 84 taxa as dominants and 60 as casuals. Most of these 144 taxa were also recorded in the present study. The observed taxa are distributed across 31 families, with Fabaceae, Asteraceae, Poaceae and Caryophyllaceae the dominant ones (Table II). Considering only the dominant taxa referred by Pinto da Silva (1971) 74

3 60 years ago, the main families were Asteraceae (25%), Poaceae (20.2%), Caryophyllaceae (8.3%), and Fabaceae (4.8%). For the casual species in the same study, Fabaceae represented 10% a value that is lower than the one recorded in the present study. In our study the three dominant families included 55% of the total surveyed taxa. This percentage was higher than in other portuguese viticultural regions, as evidenced by Cerejeira (1985) in the Ribatejo (40.7%), Barata (1987) in Palmela, Sesimbra and Setúbal (37%), Espírito Santo (1987) in Bombarral (46.7%), Ribeiro (1988) in the Douro (37%), Lopes (1989) in Bairrada (40%), Aguiar (1992) in Óbidos (41%) and Mira et al. (1999) in Évora and Borba (50%). The relationship between weed relative frequency and average species density is illustrated in Figure 1 and the corresponding values are presented in Table I. Taxa with a very high infestation degree (group ++++) were not found in Dão vineyards. Many species with a high infestation degree (group +++) were found in the surveys e.g. the annual broad-leaved species Chamaemelum fuscatum, Conyza albida, Ornithopus compressus, Spergula arvensis and Trifolium glomeratum, the annual grass species Lolium rigidum, Poa annua and Vulpia bromoides and the perennial broad-leaved species Convolvulus arvensis and Hypochaeris radicata. Most of the recorded species in the high infestation group are winter annuals whose growth season ended in late spring. Particular attention must be paid to the genus Conyza, because C. albida was found throughout the Dão region, while C. bonariensis was only observed in the Serra da Estrela and Alva sub-regions. The species in this genus frequently behave like perennials in cover-cropping systems, increasing their density annually. Controlling Conyza spp. chemically is difficult because the efficacy of the registered herbicides for vineyards is low. A considerable number of species with a medium degree of infestation (group ++) were recorded as both annuals and perennials. Most of the annual grass species were included in this group (Agrostis sp., Avena spp., Briza spp. Bromus spp., Hordeum sp. Lolium multiflorum, Poa annua, Vulpia geniculata), as were some Fabaceae species that are appropriate for cover cropping e.g. Medicago arabica, Lotus conimbricensis, Lotus hispidus (Serra da Estrela subregion only), Lupinus angustifolius ssp. reticulatus, L. gredensis, L. luteus, Ornithopus pinnatus, O. sativus ssp. isthmocarpus, Trifolium cernuum, T. incarnatum, T. michelianum, T. repens, T. resupinatum and T. vesiculosum (Table I; Figure 1). Some perennial broad-leaved species (Andryala integrifolia, Chondrilla juncea, Plantago lanceolata, Rumex pulcher) and the perennial grass Cynodon dactylon also displayed a medium degree of infestation. In general, these species were found throughout the region and seemed well adapted to the different management practices. Most of these taxa were also considered weeds by Pinto da Silva (1971) and, if improperly managed, they could be water-competitive with the vines due to their deep roots. Cynodon dactylon rhizomes can grow deep and regenerate even at 40 cm depth (Moreira, 1978). Finally, the low (+) and very low (0) infestation groups comprise about 20% of the species we found (Table I, noted only in the lower left corner of Figure 1). Effect of sub-region on weed communities Canonical correspondence analysis (CCA) revealed significant community differences among sub-regions (Figure 2). Although all the species recorded were included in the multivariate analysis, only those with the greatest ability to explain the differences between sub-regions are shown in Figure 2. The first canonical axis in the biplot of flora species explained 26.5% of the variance between sub-regions, while the second axis explained 22.3%. Based on the ordination diagram, five groups of weed species are well related with one or more particular sub-regions. The weed communities associated with the Serra de Estrela (rse = -0.71) were distinct from those linked to Besteiros (rbest = 0.85), as can be seen from its opposite position on axis 1; Terras de Senhorim (rterse = 0.70) was distinct from Alva (ralv = 0.33), based on its opposite position on axis 2. The weed communities associated with Terras de Azurara, Castendo and Silgueiros were similar, all positively related with axis 2. Having said this, many taxa have scores close to the axis origins, indicating their ubiquity in all subregions, and others were surveyed in more than, or only, one sub-region (Table I; Figure 2). The combination of the data presented by sub-region in Table I with Figure 2 revealed a large number of weed species associated with each of the five sub-regional groups. When considering the species with specific interest for cover cropping and with high value for vineyard agro-tourism, we observed that: i) The Serra da Estrela sub-region was associated with the presence of Agrotis pourretii, Vulpia geniculata, Lotus corniculatus ssp. corniculatus, L. hispidus, Ononis spinosa, Trifolium cernuum, Vicia cordata, and the Papaveraceae Papaver hybridum. ii) In the Alva sub-region Medicago sativa, Trifolium dubium and Lytrum junceum, and in Besteiros Lathyrus sylvestris, Medicago arabica, Epilobum tetragonum, Galactites tomentosa, Anagallis arvensis var. caerulea, Torilis nodosa, Ranunculus bulbosus and Myosotis persoonii, particularly stand out. iii) The following taxa were associated with the Terras de Senhorim sub-region: Trifolium nigrum, Poa bulbosa, Centhranthus calcitrapae, Filago pyramidata and Phalaris aquatica. iv) The group composed of the Terras de Azurara, Castendo and Silgueiros sub-regions was correlated 75

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